git commit d2aa1aca ("mm/init: Add 'rodata=off' boot cmdline
parameter to disable read-only kernel mappings") adds a bogus warning
to the console which states that s390 does not support kernel memory
protection.

This however is not true. We do support that since a couple of years
however in a different way than the author of the above named patch
expected.

To get rid of the misleading message implement the mark_rodata_ro
function and emit a message which states the amount of memory which
was write protected already earlier.

This is the same what parisc currently does.

We currently do not support the kernel parameter "rodata=off" which
would allow to write to the rodata section again. However since we
have this feature since years without any problems there is no reason
to add support for this.
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

We can use debug_pagealloc_enabled() to check if we can map the identity
mapping with 1MB/2GB pages as well as to print the current setting in
dump_stack.
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Acked-by: NDavid Rientjes <rientjes@google.com>
Cc: Laura Abbott <labbott@fedoraproject.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The pgtable.c file is quite big, before it grows any larger split it
into pgtable.c, pgalloc.c and gmap.c. In addition move the gmap related
header definitions into the new gmap.h header and all of the pgste
helpers from pgtable.h to pgtable.c.
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

The pmdp_xxx function are smaller than their ptep_xxx counterparts
but to keep things symmetrical unline them as well.
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

The code in the various ptep_xxx functions has grown quite large,
consolidate them to four out-of-line functions:
  ptep_xchg_direct to exchange a pte with another with immediate flushing
  ptep_xchg_lazy to exchange a pte with another in a batched update
  ptep_modify_prot_start to begin a protection flags update
  ptep_modify_prot_commit to commit a protection flags update
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

Convert the uses of pr_warning to pr_warn so there are fewer
uses of the old pr_warning.

Miscellanea:

o Align arguments
o Coalesce formats
Signed-off-by: NJoe Perches <joe@perches.com>
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

We have two close to identical report_user_fault functions.
Add a parameter to one and get rid of the other one in order
to reduce code duplication.
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

Git commit ab3f285f
"KVM: s390/mm: try a cow on read only pages for key ops"
added a fixup_user_fault to set_guest_storage_key force a copy on
write if the page is mapped read-only. This is supposed to fix the
problem of differing storage keys for shared mappings, e.g. the
empty_zero_page.
But if the storage key is set before the pte is mapped the storage
key update is done on the pgste. A later fault will happily map the
shared page with the key from the pgste.

Eventually git commit 2faee8ff
"s390/mm: prevent and break zero page mappings in case of storage keys"
fixed this problem for the empty_zero_page. The commit makes sure that
guests enabled for storage keys will not use the empty_zero_page at all.

As the call to fixup_user_fault in set_guest_storage_key depends on the
order of the storage key operation vs. the fault that maps the pte
it does not really fix anything. Just remove it.
Reviewed-by: NDominik Dingel <dingel@linux.vnet.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

The change of the access rights for an address range in the kernel
address space is currently done with a loop of IPTE + a store of the
modified PTE. Between the IPTE and the store the PTE will be invalid,
this intermediate state can cause problems with concurrent accesses.

Consider a change of a kernel area from read-write to read-only, a
concurrent reader of that area should be fine but with the invalid
PTE it might get an unexpected exception.

Remove the IPTEs for each PTE and do a global flush after all PTEs
have been modified.
Reviewed-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

When fixing the DAT off bug ("s390: fix DAT off memory access, e.g.
on kdump") both Christian and I missed that we can save an additional
stnsm instruction.

This saves us a couple of cycles which could improve the speed of
memcpy_real.
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

commit 204ee2c5 ("s390/irqflags: optimize irq restore") optimized
irqrestore to really only care about interrupts and adapted the
remaining low level users. One spot (memcpy_real) was not touched,
though - fix it. Otherwise a kdump kernel will fail while reading
the old kernel. As we re-enable irqs with a non-standard function
we have to tell lockdep about that.

Fixes: 204ee2c5 ("s390/irqflags: optimize irq restore")
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

Yet another leftover from the 31 bit era. The usual operation
"y = x & PSW_ADDR_INSN" with the PSW_ADDR_INSN mask is a nop for
CONFIG_64BIT.

Therefore remove all usages and hope the code is a bit less confusing.
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Reviewed-by: NDavid Hildenbrand <dahi@linux.vnet.ibm.com>

This is a leftover from the 31 bit area. For CONFIG_64BIT the usual
operation "y = x | PSW_ADDR_AMODE" is a nop. Therefore remove all
usages of PSW_ADDR_AMODE and make the code a bit less confusing.
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Reviewed-by: NDavid Hildenbrand <dahi@linux.vnet.ibm.com>

The ssm instruction takes longer that stnsm/stosm as it is often
used to modify DAT and PER. We know that irqsave/irqrestore only
deals with external and I/O interrupts and we know that irqrestore
can transition only from disabled->disabled or disabled->enabled,
so we can use the faster stosm.
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>

To improve readability we can use TASK_MAX_SIZE when we just check for the
upper limit.  All places explicitly dealing with 3 vs 4 level pgtables
were left unchanged.
Signed-off-by: NDominik Dingel <dingel@linux.vnet.ibm.com>
Reviewed-By: NSascha Silbe <silbe@linux.vnet.ibm.com>

By passing a non-null flag we allow fixup_user_fault to retry, which
enables userfaultfd.  As during these retries we might drop the mmap_sem
we need to check if that happened and redo the complete chain of
actions.
Signed-off-by: NDominik Dingel <dingel@linux.vnet.ibm.com>
Reviewed-by: NAndrea Arcangeli <aarcange@redhat.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: "Jason J. Herne" <jjherne@linux.vnet.ibm.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Eric B Munson <emunson@akamai.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Dominik Dingel <dingel@linux.vnet.ibm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

During Jason's work with postcopy migration support for s390 a problem
regarding gmap faults was discovered.

The gmap code will call fixup_user_fault which will end up always in
handle_mm_fault.  Till now we never cared about retries, but as the
userfaultfd code kind of relies on it.  this needs some fix.

This patchset does not take care of the futex code.  I will now look
closer at this.

This patch (of 2):

With the introduction of userfaultfd, kvm on s390 needs fixup_user_fault
to pass in FAULT_FLAG_ALLOW_RETRY and give feedback if during the
faulting we ever unlocked mmap_sem.

This patch brings in the logic to handle retries as well as it cleans up
the current documentation.  fixup_user_fault was not having the same
semantics as filemap_fault.  It never indicated if a retry happened and
so a caller wasn't able to handle that case.  So we now changed the
behaviour to always retry a locked mmap_sem.
Signed-off-by: NDominik Dingel <dingel@linux.vnet.ibm.com>
Reviewed-by: NAndrea Arcangeli <aarcange@redhat.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: "Jason J. Herne" <jjherne@linux.vnet.ibm.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Eric B Munson <emunson@akamai.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Dominik Dingel <dingel@linux.vnet.ibm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

With new refcounting we don't need to mark PMDs splitting.  Let's drop
code to handle this.

pmdp_splitting_flush() is not needed too: on splitting PMD we will do
pmdp_clear_flush() + set_pte_at().  pmdp_clear_flush() will do IPI as
needed for fast_gup.
Signed-off-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Steve Capper <steve.capper@linaro.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Tail page refcounting is utterly complicated and painful to support.

It uses ->_mapcount on tail pages to store how many times this page is
pinned.  get_page() bumps ->_mapcount on tail page in addition to
->_count on head.  This information is required by split_huge_page() to
be able to distribute pins from head of compound page to tails during
the split.

We will need ->_mapcount to account PTE mappings of subpages of the
compound page.  We eliminate need in current meaning of ->_mapcount in
tail pages by forbidding split entirely if the page is pinned.

The only user of tail page refcounting is THP which is marked BROKEN for
now.

Let's drop all this mess.  It makes get_page() and put_page() much
simpler.
Signed-off-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Tested-by: NSasha Levin <sasha.levin@oracle.com>
Tested-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Acked-by: NJerome Marchand <jmarchan@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Steve Capper <steve.capper@linaro.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Currently looking at /proc/<pid>/status or statm, there is no way to
distinguish shmem pages from pages mapped to a regular file (shmem pages
are mapped to /dev/zero), even though their implication in actual memory
use is quite different.

The internal accounting currently counts shmem pages together with
regular files.  As a preparation to extend the userspace interfaces,
this patch adds MM_SHMEMPAGES counter to mm_rss_stat to account for
shmem pages separately from MM_FILEPAGES.  The next patch will expose it
to userspace - this patch doesn't change the exported values yet, by
adding up MM_SHMEMPAGES to MM_FILEPAGES at places where MM_FILEPAGES was
used before.  The only user-visible change after this patch is the OOM
killer message that separates the reported "shmem-rss" from "file-rss".

[vbabka@suse.cz: forward-porting, tweak changelog]
Signed-off-by: NJerome Marchand <jmarchan@redhat.com>
Signed-off-by: NVlastimil Babka <vbabka@suse.cz>
Acked-by: NKonstantin Khlebnikov <khlebnikov@yandex-team.ru>
Acked-by: NMichal Hocko <mhocko@suse.com>
Acked-by: NHugh Dickins <hughd@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The normalization pass in the sorting routine of the relative exception
table serves two purposes:
- it ensures that the address fields of the exception table entries are
  fully ordered, so that no ambiguities arise between entries with
  identical instruction offsets (i.e., when two instructions that are
  exactly 8 bytes apart each have an exception table entry associated with
  them)
- it ensures that the offsets of both the instruction and the fixup fields
  of each entry are relative to their final location after sorting.

Commit eb608fb3 ("s390/exceptions: switch to relative exception table
entries") ported the relative exception table format from x86, but modified
the sorting routine to only normalize the instruction offset field and not
the fixup offset field. The result is that the fixup offset of each entry
will be relative to the original location of the entry before sorting,
likely leading to crashes when those entries are dereferenced.

Fixes: eb608fb3 ("s390/exceptions: switch to relative exception table entries")
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

Finally get rid of the leading underscore. I tried this already two or
three years ago, however Michael Holzheu objected since this would
break the crash utility (again).

However Michael integrated support for the new name into the crash
utility back then, so it doesn't break if the name will be changed
now.  So finally get rid of the ever confusing leading underscore.
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

The memory detection code historically had to use unsigned long long
since the machine reported the true memory size (>4GB) even if the
virtual machine was running in ESA/390 mode.

Since the old code is gone use unsigned long everywhere and also get
rid of an unused ADDR2G define.

(this patch converts all long longs within sclp_info to longs)

There are many more possible conversions, however that can be done if
somebody touches the corresponding code.  Since people started to
convert unrelated long types to long longs because of the types within
struct sclp_info convert this now.
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

findseg_scode is assigned, but never used.
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

address is assigned but never used.
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

While the userspace interface requests the maximum size the gmap code
expects to get a maximum address.

This error resulted in bigger page tables than necessary for some guest
sizes, e.g. a 2GB guest used 3 levels instead of 2.

At the same time we introduce KVM_S390_NO_MEM_LIMIT, which allows in a
bright future that a guest spans the complete 64 bit address space.

We also switch to TASK_MAX_SIZE for the initial memory size, this is a
cosmetic change as the previous size also resulted in a 4 level pagetable
creation.
Reported-by: NDavid Hildenbrand <dahi@linux.vnet.ibm.com>
Reviewed-by: NCornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: NDominik Dingel <dingel@linux.vnet.ibm.com>
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>

Let's annotate it correctly, so we directly get a warning if
we ever were to use it in atomic/preempt_disable/spinlock environment.
Acked-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NDavid Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

commit 1f6b83e5 ("s390: avoid z13 cache aliasing") checks for the
machine type to optimize address space randomization and zero page
allocation to avoid cache aliases.

This check might fail under a hypervisor with migration support.
z/VMs "Single System Image and Live Guest Relocation" facility will
"fake" the machine type of the oldest system in the group. For example
in a group of zEC12 and Z13 the guest appears to run on a zEC12
(architecture fencing within the relocation domain)

Remove the machine type detection and always use cache aliasing
rules that are known to work for all machines. These are the z13
aliasing rules.
Suggested-by: NChristian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

The program parameter can be used to mark hardware samples with
some token.  Previously, it was used to mark guest samples only.

Improve the program parameter doubleword by combining two parts,
the leftmost LPP part and the rightmost PID part.  Set the PID
part for processes by using the task PID.
To distinguish host and guest samples for the kernel (PID part
is zero), the guest must always set the program paramater to a
non-zero value.  Use the leftmost bit in the LPP part of the
program parameter to be able to detect guest kernel samples.

[brueckner@linux.vnet.ibm.com]: Split __LC_CURRENT and introduced
__LC_LPP. Corrected __LC_CURRENT users and adjusted assembler parts.
And updated the commit message accordingly.
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: NHendrik Brueckner <brueckner@linux.vnet.ibm.com>
Reviewed-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

Introduce /sys/debug/kernel/diag_stat with a statistic how many diagnose
calls have been done by each CPU in the system.
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

Use bit 2**1 of the pte and bit 2**14 of the pmd for the soft dirty
bit. The fault mechanism to do dirty tracking is already in place.
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

While pmem is usable as a block device or via DAX mappings to userspace
there are several usage scenarios that can not target pmem due to its
lack of struct page coverage. In preparation for "hot plugging" pmem
into the vmemmap add ZONE_DEVICE as a new zone to tag these pages
separately from the ones that are subject to standard page allocations.
Importantly "device memory" can be removed at will by userspace
unbinding the driver of the device.

Having a separate zone prevents allocation and otherwise marks these
pages that are distinct from typical uniform memory.  Device memory has
different lifetime and performance characteristics than RAM.  However,
since we have run out of ZONES_SHIFT bits this functionality currently
depends on sacrificing ZONE_DMA.

Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Jerome Glisse <j.glisse@gmail.com>
[hch: various simplifications in the arch interface]
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>

With the removal of the dynamic reallocation of page tables for
KVM (see git commit 0b46e0a3)
the page table allocation / freeing code can be simplified.

The page table free code can now use the alloc_pgste bit in the
mm context to decide if a page table is 2K or 4K, there is no mix
of different sized page tables anymore. This eliminates the need
to use "page->_mapcount == 0" to check for 4K page table.

Use the lower two bits in page->_mapcount to indicate which
2K fragments of the 4K page are in use.

As 31-bit support is gone, remove the two defines ALLOC_ORDER
and FRAG_MASK and use the constants directly where appropriate.
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

Remove two more statements which always evaluate to 'false'.
These are more leftovers from the 31 bit era.
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Reviewed-by: NDavid Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

Enable core NUMA support for s390 and add one simple default mode "plain"
that creates one single NUMA node.

This patch contains several changes from Michael Holzheu.
Signed-off-by: NPhilipp Hachtmann <phacht@linux.vnet.ibm.com>
Signed-off-by: NMichael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

With NUMA support for s390, arch_add_memory() needs to respect the nid
parameter.
Signed-off-by: NGerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

Force get_user_page() to take the slow path for NUMA migration pages.
Signed-off-by: NGerald Schaefer <geraldsc@linux.vnet.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

Heiko noticed that the current check for hugepage support on s390 is a
little bit too harsh as systems which do not support will crash.

The reason is that pageblock_order can now get negative when we set
HPAGE_SHIFT to 0.  To avoid all this and to avoid opening another can of
worms with enabling HUGETLB_PAGE_SIZE_VARIABLE I think it would be best
to simply allow architectures to define their own hugepages_supported().

Revert bea41197 ("s390/mm: make hugepages_supported a boot time
decision") in preparation.
Signed-off-by: NDominik Dingel <dingel@linux.vnet.ibm.com>
Acked-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Heiko noticed that the current check for hugepage support on s390 is a
little bit too harsh as systems which do not support will crash.

The reason is that pageblock_order can now get negative when we set
HPAGE_SHIFT to 0.  To avoid all this and to avoid opening another can of
worms with enabling HUGETLB_PAGE_SIZE_VARIABLE I think it would be best
to simply allow architectures to define their own hugepages_supported().

This patch (of 4): revert commit cf54e2fc ("s390/mm: change
HPAGE_SHIFT type to int") in preparation.
Signed-off-by: NDominik Dingel <dingel@linux.vnet.ibm.com>
Acked-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

With making HPAGE_SHIFT an unsigned integer we also accidentally changed
pageblock_order.  In order to avoid compiler warnings we make
HPAGE_SHFIT an int again.
Signed-off-by: NDominik Dingel <dingel@linux.vnet.ibm.com>
Suggested-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>